A cage allows fish to be moved under water in a river from a hatchery to a location at or near the rivers mouth. The cage side walls contain openings which allow water to pass through the cage as it is towed downstream but prevent the fish from swimming out of the cage. A first flotation device supports the cage submerged where it is filled with fish and then towed downstream to where the fish are released. A second flotation device has passageways which allow filling it with either air or water. When filled with water it has no buoyancy effect on the cage. However, when filled with air the second flotation device raises the cage to where its bottom is at or near the water surface and it can be towed upstream with reduced drag.
